invalid memory access error in mixed cluster

In mixed cluster, when one of the nodes supports collections, it is possible that the library would interpret standalone buffer that stores header with key and updated collection id.

reproduction steps

1. setup two node cluster with version 6.6-stable
2. run another node with version 7.1-stable
3. join 7.1-stable with the rest
4. find a key that assigned to one of the vbuckets on 7.1-stable (cbc-keygen generates list of keys distributed across vbuckets, cbc-hash displays node where the given key is stored)
5. bootstrap libcouchbase using address of the 7.1-stable
6. execute kv operation using the key found previously

observed behavior

the application terminated because of illegal memory access

expected behavior

the application completes without any errors